Yes we need to know what version hp-ux is running on your system and let us know what type swapping you want to do.
a) file system
b)device swapping
c) End of the disk space
Depending on that we can put the solution if needed for your system

I have already described how to do filesystem swap:
device swapping is totally different from file system swapping

I am now giving you device swapping example. First of all you have to search for a unused disk and after ensuring the disk is not having any entry in the /etc/lvmtab then you can execute
pvcreate /dev/rdsk/cxtydz
swapon /dev/dsk/cxtydz
then put the entry in the /etc/fstab
/dev/dsk/cxtydz - swap defaults 0 0